Method and device for regulating a regulating circuit

ABSTRACT

For a closed-loop feedback control of a controlled system having a predetermined set course and a control trajectory for use in controlled systems in motor vehicles, an output trajectory of the controlled system is measured for the entire control time in which the control trajectory is applied to the controlled system, an error of the controlled system is detected as a function of predetermined set course and the output trajectory, and a new control trajectory is calculated for each instant of a later control process as a function of the error and the control trajectory.

The invention relates to a method for the closed-loop feedback controlof a controlled system having a predetermined set course and a controldevice for processes having a predetermined set course.

Methods for the closed-loop feedback control of motor drives aresufficiently known. Such controlled systems are used sufficiently inmotor vehicles in particular, as in electrically actuated windowlifters, seat controls, sliding doors, and/or speed control of wipersystems, for example. In a particular class of these control processes,the set course or a set trajectory of the controlled system is preset.The set course is to be followed repeatedly using the control process orthe control device. The individual control processes can hereby beseparated by longer time intervals. Such control processes having apredetermined set course are used widely in motor vehicles inparticular. In electrically actuated window lifters, seat controls orsliding doors, and in the speed control of a wiper system, for instance.

A multitude of closed-loop feedback controls are made known in therelated art. For example P, PI, PID controllers (proportional,proportional+integral, proportional+integral+differential), statuscontrollers, adapter controllers are used for correction purposes alongpreset set courses. A change in the controlled system (actuator)presents particular difficulties for a control process. The quality ofthe control process is greatly diminished to a certain extent bychanges, such as wear or ageing or parameter fluctuations caused by anyother means. More complex control methods (adaption), which can takesuch changes into consideration, are very limited due to the highrequirement on available computer power. Adapter methods often requirean overproportionally high cost and material expenditure when used withsimple and the simplest control processes in particular.

In light of this related art, the invention is based on the problem ofproviding a method and a control device that allow simple and reliableclosed-loop feedback control of recurrent processes and can thereby takechanges and varying influences of the controlled system intoconsideration.

The problem is solved according to-the invention by a method for theclosed-loop feedback control of a controlled system having apredetermined set course and a control trajectory, whereby an outputtrajectory of the controlled system is measured for the entireclosed-loop feedback control time in which the control trajectory isapplied to the controlled system, an error of the controlled system isdetermined as a function of the set course and the output trajectory,and, finally, a new control trajectory is calculated for each instant ofa later control process as a function of the error and the controltrajectory. This method is based on the approach that a predeterminedset course and a first predetermined control trajectory are present.

By comparing the actual output trajectory of the controlled system withthe set course, the method according to the invention determines a newcontrol trajectory that draws the output trajectory near to the setcourse. In this method, the set course and the control trajectory canhave values that change over time, as well as constant values. Moreover,transient processes of the controlled system can also be taken intoaccount in the control trajectory.

According to the invention, the output trajectory of the controlledsystem is measured for the entire closed-loop feedback control time inwhich the control trajectory is applied to the controlled system. Theoutput trajectory and the set course serve to determine the error. Theerror is generally a measure of the deviation between the actual and setcourse of the controlled system. Time shifts/delays and othertime-related phenomena of the controlled system can be taken intoconsideration in the determination of the error. According to thepresent invention, the new control trajectory is determined individuallyfor every instant of a later control process. A new value of the controltrajectory is calculated for a certain instant as a function of theerror and the control trajectory, whereby the calculation is based onthat error that was determined during application of the controltrajectory with the aid of the measured actual values. An advantage ofthis method is that the great complexity of an adaptive method isavoided. The new control trajectory can be calculated at every instantin a simple manner, whereby no complex analyses, such as wavelet orFourier transformations, are necessary.

In an embodiment of the method that further reduces the computingeffort, the later control process, for which the new control trajectoryis calculated, follows the control process in which the error wasdetermined. In other words, the new control trajectory is alwayscalculated for the subsequent control process. As a result, costlyassignments between different control processes are avoided. With regardfor this process step, it is given that the same set point course ispreset again for the subsequent control process.

The computing effort is reduced particularly markedly in an advantageousfurther development of the method in which the value of the new controltrajectory is determined in an instant of the subsequent control processfrom the values of the closed-loop control error and the controltrajectory at an instant of the preceding control process, whereby thesame length of time since a beginning instant in which the controltrajectory was applied to the controlled system has transpired in theinstants of each of the two control processes. Accordingly, the newcontrol trajectory at an instant t is determined from the originalcontrol trajectory and the error in an instant t¹ from the precedingcontrol interval. This relationship can be illustrated using thefollowing formula:

 u _(k+m)(t)=φ_(u)(u _(k)(t ¹))⊕φ_(e)(e_(k)(t′)),

whereby t−T _(k+m) =t′−T _(k)  Formula 1:

In this case, T_(k) and T_(k+m) represent the start of the k^(th) or the(k+m)^(th) control process, u_(k) (·) represents the control trajectoryof the k^(th) process, e_(k) (·) represents the error in the k^(th)control process, and u_(k+m) (·) represents the control trajectory forthe (k+m)th control process.

In the advantageous further development of the method, φ_(u,e) aresymbols that assign a new value to a value of the control trajectoryand/or the error. It proves extremely advantageous for the arithmeticalimplementation of this process that φ can be a function. In contrast, φis often used as a functional, i.e., as a symbol of a function on a newfunction, in adaptive methods and/or other closed-loop feedback controlshaving a preset set course. Such a functional control relationshipplaces high requirements on the control process and its implementation.As mentioned previously, the control relationship above can besimplified further using m=1.

The evaluation of the function values φ_(u,e) can take place using asuitable circuit or a microprocessor. The combination of the functionvalues ⊕ can thereby take place using a suitable selected circuit aswell.

In a further simplification of the method, which also reduces thecomputing effort again and increases the robustness of the calculation,the value of the new control trajectories (u_(k+1)) are determined fromthe sum of a first and a second value, whereby the first value is only afunction of the value of the control trajectory (φ_(u)), and the secondvalue is only a function of the value of the error (φ_(e)) The use ofaddition—element-wise addition in the case of multicomponent controltrajectories—leads to a simple implementation of the controlrelationship with an adder. Moreover, addition has the advantage thatdetection errors in the determination of the error do not strengthen e,and the method can therefore be designed to be robust.

In the method according to the invention, it proves advantageous tocalculate the value of the new control trajectory from the sum of thevalue of the old control trajectory and the error multiplied by a realfactor K. In other words, the function φ_(u) is therefore selected as anidentity symbol, and the function φ_(e) is selected as multiplication bya factor K. If multicomponent control trajectories and/or multicomponenterrors are considered, element-wise multiplication and element-wiseaddition take place. In the case of a multicomponent error, amulticomponent real factor K can also be provided, which is multipliedelement-wise by the error e.

It has proven appropriate to select the value of the factor K≧0. With amulticomponent factor K, each component is selected greater than zero(≧0). In a summary of the further developments of the method accordingto the invention described above, the following control relationshipresults:

u _(k+1)(t)=u_(k)(t)+K e _(k)(t′),

whereby t−T _(k+1) =t′−T _(k) and K≧0  Formula 2:

Implementation of such a control relationship is extremely simple,especially since the amplification factor K can be carried out using asimple amplification circuit, and the addition can be carried out usinga traditionally known adder.

In a further development of the method, the new control trajectory iscalculated after completion of the control process in which the errorwas determined. This makes it possible to calculate the new controltrajectory without a real-time requirement. Since sufficient computingtime can be made available between two control processes for thecomputing process, the method described is an iteratively learningclosed-loop feedback control in which no adaptation takes place duringthe control process.

In an appropriate further development, a predetermined set course can beselected from various predetermined set courses. It must then be takeninto consideration that the selected set course must be included in thedetermination of the new control trajectory. To ensure clarity, thedependence on the set course selected—which is represented by the errore—is not reflected in the formulas above.

It proves to be particularly advantageous to store the set course,control trajectory, and error as sampled time series and to make themavailable to the method. The sampling rate in this case depends on theprocess to be controlled and the controlled system. In the methodaccording to the invention, time characteristics can also be processedas functions, of course, either as an explicit time function or animplicit time function that is given as a solution to a differentialequation, for example.

It proves appropriate to sample the time series at equal intervals.

According to the invention, the object is also solved using a controldevice for processes having a predetermined set course, whereby thecontrol device comprises at least one storage means and a controller onwhich the set point course, a control trajectory, and an outputtrajectory of a controlled system belonging to the control trajectoryare contained as input signals, which calculates a new controltrajectory and stores it in the storage means, whereby the outputtrajectory and the control trajectory are also stored in the storagemeans. In the control device according to the invention, the controllerdetermines a new set point course for the subsequent control process.

The signal values of the set course, the control trajectory, and theoutput trajectory are contained on the controller. The output trajectoryis measured as the actual course of the controlled system while thecontrol signal is applied. The control trajectory newly calculated inthis manner is stored in the storage means, from which it is applied tothe controlled system in a subsequent control process. The last controltrajectory applied to the controlled system and the output valuesmeasured by the controlled system are also stored in the storage means.

In an embodiment of the control device according to the invention thatsimplifies the design of the controller, the values of the set pointcourse, the output trajectory, and the control trajectory from aninstant of the preceding control process are contained on thecontroller. As explained above, this reduces the calculation of a newcontrol trajectory to the simple combination of values. Complexcombinations that take the course of the trajectory into considerationor require transformations of the time format, are avoided with thiscontroller. This reduces the hardware complexity of the controller.

The control device appropriately comprises three storage means. Amodular design of the storage components is achieved as a result, sothat the control device can be installed easily and manufactured withminimal material costs. According to the invention, the controller ofthe control device calculates the control trajectory according to one ofthe methods described previously.

A particularly advantageous embodiment of the invention will beillustrated and explained with reference to the sole figure.

The control device comprises a controller 1 and three storage means 2,3, 4. Controller 1 and storage means 2 are connected by way of a line 9in such a manner that the controller 1 can store a control trajectory inthe storage means 2. The storage means 3 is connected with thecontroller 1 by way of a line 8 so that control values can be stored onthe controller 1. The storage means 4 is connected with the controller 1by way of a line 7 in such a manner that its storage contents aredelivered to the controller 1. The control trajectory from the storagemeans 3 is stored on a controlled system 5 by way of a line 11. Theactual value of the controlled system 5 is measured and written in thestorage means 4 by way of a line 10. From there it is fed to thecontroller 1 by way of the line 7.

If the controller 1 has calculated a new control trajectory u_(k+1)(t)and stored it in the storage means 2, the control trajectory is thencopied from the storage means 2 into the storage means 3 by way of aline 12. In the subsequent (k+l)^(th) control process, the controltrajectory from storage means 3 is applied to the controlled system 5.

The predetermined set point is delivered externally from a furtherstorage means (not shown) to the controller 1 by way of a line 6. Sensorinformation, such as signals from humidity sensors used with awindshield wiper control, can be taken into consideration as well in thepredetermined set point.

The closed-loop feedback control takes place in that the actual valuesof the quantity to be controlled are measured during the control processusing a digital computer (not shown), for example. Continuous quantitiesare sampled for this purpose. The time series sampled in this manner isstored in storage means 4. The control variable or control quantityapplied to the process is stored in storage means 3. The set quantity isapplied to the controller 1 by way of the line 6 in closed form or as asampled time series so that the controller 1 can determine a controltrajectory.

The process typically runs in fixed time intervals 0 through T. Thesampling can take place at equal or different intervals and is usuallynot varied from control process to control process.

If a control process is completed, the measured courses from the storagemeans are used to calculate the entire set trajectory and/or controltrajectory for the next process according to the control principle.Individual values of the trajectory and the error course can hereby bycontained on the controller 1 by way of the inputs 6, 7, 8. Thistrajectory is stored in storage means 2.

The control variables are copied from storage means 2 to storage means3. If the next process is started, the corresponding control variablesare read from the storage means 3 and applied to the process of thecontrolled system 5. In terms of measured signal processing, it isparticularly advantageous that signals are not processed during theprocess. Consequently, non-causal operations, such as non-causal digitalfilters, can be used. In addition, a smoothing of the measured curvescan be achieved without delaying the control process.

What is claimed is:
 1. Method for a closed-loop feedback control of acontrolled system having a predetermined set course and a controltrajectory for use in controlled systems in motor vehicles, whereby anoutput trajectory of the controlled system is measured for an entirecontrol time in which the control trajectory is applied to thecontrolled system, an error of the controlled system is detected as afunction of the predetermined set course and the output trajectory, anda new control trajectory is calculated for each instant of a latercontrol process as a function of the error and the control trajectory.2. Method according to claim 1, characterized in that the later controlprocess for which the new control trajectory is calculated follows acontrol process in which the error was determined.
 3. Method accordingto claim 2, characterized in that the value of the new controltrajectory is determined in an instant of a subsequent control processfrom the values of the error and the control trajectory at an instant inthe preceding control process, whereby the same virtual time hastranspired since a beginning instant in which the control trajectory wasapplied to the controlled system in the instants of each of the twocontrol processes.
 4. Method according to claim 3, characterized in thatthe value of the new control trajectory is determined from the sum of afirst and a second value, whereby the first value is a function of thevalue of the control trajectory, and the second value is a function ofthe value of the error.
 5. Method according to claim 4, characterized inthat the value of the new control trajectory is calculated from the sumof the value of an old control trajectory and the error multiplied by areal factor (k).
 6. Method according to claim 5, characterized in thatthe value of the factor (k) is greater than
 0. 7. Method according toclaim 1, characterized in that the new control trajectory is calculatedafter completion of the control process in which the error wasdetermined.
 8. Method according to one of the claim 1, characterized inthat the predetermined set course is selected from various possible setcourses.
 9. Method according to one of the claim 1, characterized inthat the set course, the control trajectory, and the error are stored assampled time series.
 10. Method according to claim 9, characterized inthat the time series are sampled at the same intervals.
 11. Controldevice according to claim 10, characterized in that the controllercalculates the new control trajectory using a method for a closed-loopfeedback control of a controlled system having a predetermined setcourse and a control trajectory for use in controlled systems in motorvehicles, whereby an output trajectory of the controlled system ismeasured for the entire control time in which the control trajectory isapplied to the controlled system, an error of the controlled system isdetected as a function of predetermined set course and the outputtrajectory, and a new control trajectory is calculated for each instantof a later control process as a function of the error and the controltrajectory.
 12. Control device for processes having a predetermined setcourse, comprising at least one storage means, and a controller to whicha set course is submitted via a line, an output trajectory is submittedvia an actual value input, and a control trajectory is submitted via acontrol signal input, wherein the output trajectory is stored in a firststorage means while the control trajectory is stored in a second storagemeans.
 13. Control device according to claim 12, characterized in thatvalues of the set course, the output trajectory, and the controltrajectory from one instant of a past control process are contained onthe controller at the same time.
 14. Control device according to claim12, characterized in that three storage means are provided.